This invention relates to a process for the production of antimonate-based mixed metal oxide catalysts and the catalysts produced therefrom. This invention further relates to use of the antimonate-based mixed metal oxide catalysts of the invention in reactions for the ammoxidation or oxidation of organic compounds.
It is known that antimony-containing metal oxide catalysts, specifically those comprising the oxides of antimony and at least one metal selected from the group consisting of iron, cobalt, nickel, tin, uranium, chromium, copper, manganese, titanium, and cerium are useful for the production of aldehydes and carboxylic acids through oxidation of organic compounds, i.e. olefins, the production of dienes, unsaturated aldehydes and unsaturated acids through oxidative dehydrogenation of olefins, and the production of nitriles through ammoxidation of olefins, alcohols and aldehydes.
Various catalytic processes are known for the oxidation or ammoxidation of olefins. Such processes commonly react an olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant, and for the production of methacrolein and methacrylonitrile, isobutene is the generally used olefin reactant.
Many catalysts are disclosed as suitable in the oxidation and/or ammoxidation of olefins, including those catalysts disclosed in U.S. Pat. Nos. 5,094,990; 4,590,175; 4,547,484; 4,487,850; and 4,413,155. One such catalyst is described in U.S. Pat. No. 4,547,484. This catalyst is represented by the empirical formula:SbaUbFecBidMocOfwherein a is 1 to 10, b is 0.1 to 5, c is 0.1 to 5, d is 0.001 to 0.1, e is 0.001 to is a number taken to satisfy the valence requirements of Sb, U, Fe, Bi, and Mo in the oxidation states in which they exist in the catalyst. The processes for preparing these catalysts involve the addition of solid, generally powdered, antimony, added as antimony metal or Sb2O3 to the reactor.
Although the yield and selectivity of the above-described catalysts are generally satisfactory, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the conversion of the reactant(s), the yield of the desired product(s), and the stability of the catalyst during operation. In many cases, a reduction in the cost of a catalyst system on the order of a few cents per pound or a small percent increase in the yield of the desired product represents a tremendous commercial economical advantage. Since it is well known that the economics of acrylonitrile manufacture dictate increasingly higher yields and selectivity of conversion of reactants to acrylonitrile in order to minimize the difficulties attending the purification of the product and handling of large recycle streams, research efforts are continually being made to define new or improved catalyst systems and methods and processes of making new and old catalyst systems to reduce the cost and/or upgrade the activity and selectivity of such catalyst systems. A catalyst having improved reproducibility and homogeneity, and containing substantially less α-Sb2O4 while having equivalent or better catalyst performance is desired. The discovery of the improved catalysts of the present invention and the method of preparing the improved catalysts of the present invention is therefore believed to be a decided advance in the state of the art.